The effect of substrate temperature on the composition and growth of tantalum oxide thin films deposited by plasma-enhanced chemical vapour deposition

Abstract

Tantalum oxide (Ta 2O 5) thin films were deposited on silicon substrates by plasma-enhanced chemical vapour deposition using tantalum ethylate (Ta(C 2H 5O) 5) and nitrous oxide (N 2O). The growth rate of the tantalum oxide thin films showed Arrhenius behaviour and the apparent activation energy was 3.75 kcal mol −1. The composition of tantalum oxide, determined from Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy analyses, showed a dependence on the substrate temperature. The refractive index of the tantalum oxide thin films measured by ellipsometry showed a strong relation to the composition of thin films, However, the growth rate and composition of the thin films were somewhat independent of the r.f. input power. The deposition behaviour of tantalum oxide films was regarded as the competitive reaction between the tantalum-containing species and oxidant species on the silicon substrate surface. The structure of the deposited films was amorphous, but it changed to a polycrystalline structure after annealing at 900°C in a N 2 ambient. The electrical properties of the deposited films were also characterized by capacitance-voltage and current-voltage characteristics.